In general, a compressor is a mechanical apparatus for compressing the air, refrigerant or other various operation gases and raising a pressure thereof, by receiving power from a power generation apparatus such as an electric motor or turbine. The compressor has been widely used for an electric home appliance such as a refrigerator and an air conditioner, or in the whole industry.
The compressors are roughly classified into a reciprocating compressor in which a compression space for sucking or discharging an operation gas is formed between a piston and a cylinder, and the piston is linearly reciprocated inside the cylinder, for compressing a refrigerant, a rotary compressor in which a compression space for sucking or discharging an operation gas is formed between an eccentrically-rotated roller and a cylinder, and the roller is eccentrically rotated along the inner wall of the cylinder, for compressing a refrigerant, and a scroll compressor in which a compression space for sucking or discharging an operation gas is formed between an orbiting scroll and a fixed scroll, and the orbiting scroll is rotated along the fixed scroll, for compressing a refrigerant.
Recently, a linear compressor which can improve compression efficiency and simplify the whole structure without a mechanical loss resulting from motion conversion by connecting a piston directly to a linearly-reciprocated driving motor has been popularly developed among the reciprocating compressors.
FIG. 1 is a view illustrating a conventional linear compressor. FIG. 2 is a view illustrating the linear compressor of FIG. 1 as viewed from the back cover. In the linear compressor 1, the piston 30 is linearly reciprocated in a cylinder 20 by a linear motor 40 inside a hermetic shell 10, for sucking, compressing and discharging a refrigerant. The linear motor 40 includes an inner stator 42, an outer stator 44, and a permanent magnet 46 disposed between the inner stator 42 and the outer stator 44, and linearly reciprocated by a mutual electromagnetic force. As the permanent magnet 46 is driven in a state where it is coupled to the piston 30, the piston 30 is reciprocated linearly inside the cylinder 20 to suck, compress and discharge the refrigerant.
The linear compressor 1 further includes a frame 52, a stator cover 54, and a back cover 56. The linear compressor may have a configuration in which the cylinder 20 is fixed by the frame 20, or a a configuration in which the cylinder 20 and the frame 52 are integrally formed. At the front of the cylinder 20, a discharge valve 62 is elastically supported by an elastic member, and selectively opened and closed according to the pressure of the refrigerant inside the cylinder. A discharge cap 64 and a discharge muffler 66 are installed at the front of the discharge valve 62, and the discharge cap 64 and the discharge muffler 66 are fixed to the frame 52. One end of the inner stator 42 or outer stator 44 as well is supported by the frame 52, and an O-ring or the like of the inner stator 42 is supported by a separate member or a projection formed on the cylinder 20, and the other end of the outer stator 44 is supported by the stator cover 54. The back cover 56 is installed on the stator cover 54, and a muffler 70 is positioned between the back cover 56 and the stator cover 54.
Further, a supporter piston 32 is coupled to the rear of the piston 30. Main springs 80 whose natural frequency is adjusted are installed at the supporter piston 32 so that the piston 30 can be resonantly moved. The main springs 80 are divided into front springs 82 whose both ends are supported by the supporter piston 32 and the stator cover 54 and rear springs 84 whose both ends are supported by the supporter piston 32 and the back cover 56. The conventional linear compressor includes four front springs 82 and four rear springs 84 at longitudinally and laterally symmetrical positions. Accordingly, the number of main springs 82 to be provided and the positional parameters to be controlled in order to maintain balance upon movement of the piston 30 are eight, respectively. Consequently, the manufacturing process becomes complicated and longer and the manufacturing cost is high due to a large quantity of main springs and a large number of parameters to be controlled.